Fuel cells are electrochemical cells that are being developed for mobile and stationary electric power generation. One fuel cell design uses a solid polymer electrolyte (SPE) membrane or proton exchange membrane (PEM), to provide ion transport between the anode and cathode. Gaseous and liquid fuels capable of providing protons are used. Examples include hydrogen and methanol, with hydrogen being favored. Hydrogen is supplied to the fuel cell anode. Oxygen (as air) is the cell oxidant and is supplied to the cell's cathode. The fuel cell electrodes are formed of porous conductive materials, such as woven graphite, graphitized sheets, or carbon paper to enable the fuel to disperse over the surface of the membrane facing the fuel supply electrode. Each electrode comprises finely divided catalyst particles (for example, platinum particles), supported on carbon particles, to promote ionization of hydrogen at the anode and reduction of oxygen at the cathode. Protons flow from the anode through the ionically conductive polymer membrane to the cathode where they combine with oxygen to form water, which is discharged from the cell. Conductor plates carry away the electrons formed at the anode.
Currently, state of the art PEM fuel cells utilize a membrane made of perfluorinated ionomers such as Dupont NAFION®. The ionomer carries pendant ionizable groups (e.g. sulfonate groups) for transport of protons through the membrane from the anode to the cathode.
Currently, platinum (Pt) supported on a high surface area carbon is the most effective electrocatalyst for PEM fuel cell systems. However, a significant problem hindering large-scale implementation of proton exchange membrane (PEM) fuel cell technology is the loss of performance during extended operation and automotive cycling. Recent investigations of the deterioration of cell performance have revealed that a considerable part of the performance loss is due to the degradation of the electrocatalyst. Although carbon has been considered as the most favorable catalyst support because of its low cost, good electron conductivity, high surface area, and chemical stability, corrosion of carbon supports on the cathode side of PEM fuel cells is emerging as a challenging issue for long-term stability of PEM fuel cells.
It is an object of this invention to provide a porous titanium oxide electrocatalyst support having suitable properties for a PEM fuel cell environment including suitable surface area, electrical conductivity and chemical stability.